Study on regional distribution of land surface parameters and components of surface radiation balanceover South Ningxia
宁南地区地表特征参数及辐射平衡区域分布

Dealing with regional land surface parameters and radiation balance components is a very important and difficult task.Studying on land surface parameters and components of surface radiation balance over inhomogeneous landscape,the utilization of satellite remote sensing is indispensable.In this study,a parameterization method based on Landsat-7 ETM data and 22 weather stations data is described for deriving the regional distributions of land surface parameters(NDVI,surface reflectance,surface temperature) and components of surface radiation balance(surface absorbed shortwave radiation,surface upward longwave radiation,downward atmospheric radiation,net radiation) over the southern Ningxia region.Distribution map and histograms of the parameters and components are given.Furthermore,the southern Ningxia region is classified into five surface types,regional distributions of land surface parameters and components of surface radiation balance are discussed according to each type.The results indicate:(1) All the regional distributions are characteristic in their terrain nature and the regional distributions are obvious and regular.The maps of mountains and rivers are very clear with dense vegetations growing on the mountains and by the rivers.It is seen that the derived regional distributions of land surface parameters and components of surface radiation balance for the whole mesoscale area are well in accord with the land surface status.(2) The maximum NDVI is on the Liupan mountains(with a forest) followed by the Yueliang mountain and rivers and other irrigated areas(with grass or crops),and the low NDVI value area over water bodies and nudation.(3)The regional distributions of surface reflectance and surface temperature are basically in-phase opposition with the corresponding regional distributions of NDVI.(4)The surface absorbed shortwave radiation is high over the Liupan mountain,the Yueliang mountain and by the rivers,and the nudation is low.On clear day,the surface absorbed shortwave radiation is mainly determined by surface reflectance.The regional distribution of net radiation is similar to the surface absorbed shortwave distribution.